Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or a bag mask apparatus, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about 25% to 30% of normal blood flow. However, even experienced paramedics cannot maintain adequate chest compressions for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successful at sustaining or reviving the patient. Nevertheless, if chest compressions could be adequately maintained, then cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended CPR efforts (45 to 90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. In one variation of such devices, a belt is placed around the patient's chest and an automatic chest compression device tightens the belt to effect chest compressions. Our own patents, Mollenauer et al., Resuscitation device having a motor driven belt to constrict/compress the chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Bystrom et al., Resuscitation and alert system, U.S. Pat. No. 6,090,056 (Jul. 18, 2000); Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002); and our application Ser. No. 09/866,377 filed on May 25, 2001, our application Ser. No. 10/192,771, filed Jul. 10, 2002 and our application Ser. No. 12/726,262, filed Mar. 17, 2010 show chest compression devices that compress a patient's chest with a belt. Each of these patents or applications is hereby incorporated by reference in their entireties.
Since seconds count during an emergency, any CPR device should be easy to use and facilitate rapid deployment of the device on the patient. Our own devices are easy to deploy quickly and may significantly increase the patient's chances of survival.
One important aspect of such devices is the need for small, powerful yet reliable power supply to power the device. However, such a need is not limited to mechanical compression devices such as those described above. There are many medical devices which require a light weight power supply, typically a battery, which must be capable of delivering sufficient energy to the device for an extended period of time. Moreover, the power supply must be relatively light weight, so as to enhance portability of the medical device, yet it must deliver its power for an extended period of time without significant voltage or current drop off to ensure consistency of operation throughout the period the device is being used.
Modern batteries typically require additional electronic circuitry or a battery management system designed to manage the operation of the battery. Such a battery management system should be able to monitor the operation of the battery, including charging and discharging of the battery without significantly adding to the internal resistance of the battery. Moreover, a battery management system should also be capable of accommodating different battery chemistries as battery technology evolves. To accomplish this, the battery management system will also need to have sufficient processing power and memory capacity to record events that occur during the lifetime of the battery, and to be able to analyze and/or communicate data related to those events to a centralized or distributed server system for analysis. The battery management system will also include various safety related systems designed to protect the battery, the devices being powered by the battery, and users of the battery or powered device from various environmental or operational factors that may occur. The present invention satisfies these, and other needs.